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<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Document</title>
</head>

<body>
<script>
    // 原型对象的应用 扩展内置对象方法

    Array.prototype.sum = function () {
        var sum = 0;
        for (var i = 0; i < this.length; i++) {
            sum += this[i];
        }
        return sum;
    };
    // Array.prototype = {
    //     sum: function() {
    //         var sum = 0;
    //         for (var i = 0; i < this.length; i++) {
    //             sum += this[i];
    //         }
    //         return sum;
    //     }

    // }
    var arr = [1, 2, 3];
    console.log(arr.sum());
    console.log(Array.prototype);
    var arr1 = new Array(11, 22, 33);
    console.log(arr1.sum());
</script>
</body>

</html>
